1. Field of the Invention
The present invention relates to a two-equivalent yellow coupler having improved color developing properties, color photographic photosensitive materials containing said coupler, and an image-forming method using this type of coupler.
2. Description of the Prior Art
In color photosensitive materials, it is highly desired to form a color image showing a high sensitivity, a high gamma value and a high contrast, and a fundamental way of achieving this is to select an appropriate group for elimination (i.e., coupling-off group) when using a two-equivalent coupler. Of course, the other properties of the coupler should not be sacrificed in the accomplishment of this purpose. Examples of such coupling-off groups are aryloxy groups as disclosed in U.S. Pat. No. 3,408,194, acyloxy groups as described in U.S. Pat. No. 3,447,928, imido groups as described in Japanese Patent Application (OPI) Nos. 26133/72 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") and 13576/74, triazolyl groups as described in Japanese Patent Application (OPI) No. 17438/76, tetrazolyl groups as described in Japanese patent application (OPI) No. 145319/76, aminosulfonyloxy groups as described in Japanese Patent Publication No. 12661/74, sulfinyloxy groups as described in Japanese patent publication No. 12660/74, benzotriazolyl groups as described in British Pat. Nos. 1,450,479 and 1,476,760, and pyrazolyl groups as described in U.S. Pat. No. 4,049,458.
But U.S. Pat. No. 4,049,458 does not disclose an aryl group substituted with an alkoxycarbonyl group for R.sub.4 in a formula (I) thereof.
Further, most of these coupling-off groups are not entirely satisfactory, due to various disadvantages, such as inadequate reactivity in the coupling reaction, poor dispersibility (which causes difficulties in coating), color fogging, difficulties in coupler synthesis, poor stability of the color image formed, and poor shelf life of the coupler.